Christmas Day

Christmas Day Holiday Period Estimate for 2021

A frequently asked question is “How much more dangerous is travel over the Christmas Day holiday?” Two aspects of this question must be considered: “Compared to what?” and “What about changes in the amount of driving?”

NSC generally compares the holiday to periods of similar length before and after the holiday. However, because New Year’s Day is exactly one week after Christmas, we chose to compare Christmas to periods of similar length one week and two weeks before it. Specifically, from 6 p.m. Thursday to 11:59 p.m. Sunday of the two weeks immediately before the Christmas Day weekend. This chart shows the fatality data from FARS for 1995 to 2019 for comparable weekends. The average number of traffic deaths during the Christmas Day holiday period over the last six 3.25-day holiday periods is 9.8% lower than the average number of traffic deaths during the comparison periods (297 vs. 329 deaths). The difference between these two means is not statistically significant.

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Source: NSC analysis of NHTSA FARS data

 

NSC also compares the Christmas Day holiday to other holiday periods. When comparing holiday periods of different lengths, an average fatality per day rate is used. The summer holidays tend to have higher average fatality rates per day than winter holidays. In 2019 (latest available final data), the Christmas holiday experienced a higher average daily fatality rate than the other two winter holidays but far lower than the summer holidays.

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  • Data Table

Source: NSC analysis of NHTSA FARS data

 

The second question concerns changes in the amount of travel or exposure. NSC is not aware of any data system that tracks changes in vehicle miles of travel by day of the year on a national basis. Lacking an objective measure of exposure change, NSC assumes travel is greater on holiday weekends than on non-holiday weekends. If that is in fact true, then with greater travel and fewer deaths, the risk of dying in a traffic crash during the Christmas Day holiday period is less than comparable non-holiday periods.

Estimate methods

The objective is to estimate the number of deaths that will occur in traffic crashes during the Christmas Day holiday period based on data available several weeks before the holiday. The estimate developed by NSC includes all traffic deaths from crashes during the holiday period.

The general procedure involves three steps. First, historical data are used to determine the average fraction that holiday fatalities are of the total motor-vehicle deaths for the month. Second, total traffic deaths for the coming month in which the holiday falls are estimated using a time series forecasting model. Third, the projected total for the month is multiplied by the fraction to obtain the holiday estimate.

Holiday as percent of monthly fatalities: Total December motor-vehicle deaths are calculated using the latest six years of final data available from the National Center for Health Statistics (NCHS). Traffic fatality estimates for the Christmas Day holiday period are calculated using data from NHTSA’s FARS.

The table shows total motor-vehicle fatalities for December and traffic fatalities from crashes that occurred during the holiday period. Over the six 3.25-day Christmas Day holiday periods recorded since 2006, fatalities from crashes during the holiday period averaged 9.2% of the total fatalities in December.

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A time series model was developed to forecast an estimate of total traffic deaths for December 2021. An exponential smoothing model with seasonality was constructed based on monthly traffic deaths recorded through October 2021. This model was chosen because of the seasonal pattern in traffic deaths. The model forecasts total traffic fatalities for December 2021 to be 4,029. Multiplying the projected total fatalities by the fraction obtained in the first step gives an estimate of 371 traffic fatalities from crashes during the holiday period.

The 90% confidence interval for the estimate of total December motor-vehicle deaths is 3,625 to 4,433. If we assume the fraction of December deaths that occur during the Christmas Day holiday period is normally distributed, then the 90% confidence interval for that fraction is 8.68% to 9.73%. Combining these two estimates gives the confidence interval for the Christmas Day holiday period estimate: 314 to 431 traffic deaths.